If a TreeItem gets added to a TreeView it is not immediately programmatically editable. It looks like the treeview is updated to late.


FXML:
<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.geometry.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.HBox?>


<BorderPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.SimpleController">
   <center>
      <TreeView fx:id="tree" prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER" />
   </center>
   <top>
      <Button mnemonicParsing="false" onAction="#createItem" text="create item" BorderPane.alignment="TOP_LEFT" />
   </top>
</BorderPane>

Main.java
package application;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(final Stage primaryStage) {
        try {
            FXMLLoader fxmlLoader = new FXMLLoader(this.getClass().getResource("Test.fxml"));
            fxmlLoader.load();
            Scene scene = new Scene(fxmlLoader.getRoot(), 300, 200);
            primaryStage.setScene(scene);
            primaryStage.setTitle("Test");
            primaryStage.show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(final String[] args) {
        Application.launch(args);
    }
}

SimpleController.java:
package application;

import javafx.fxml.FXML;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.control.cell.TextFieldTreeCell;
import javafx.util.converter.DefaultStringConverter;

public class SimpleController {

    @FXML
    private TreeView<String> tree;

    public void initialize() {
        this.tree.setEditable(true);
        this.tree.setCellFactory(p -> new TextFieldTreeCell<>(new DefaultStringConverter()));

        TreeItem<String> root = new TreeItem<>();
        root.setValue("Items");
        root.setExpanded(true);

        this.tree.setRoot(root);
    }

    @FXML
    public void createItem() throws InterruptedException {
        TreeItem<String> newItem = new TreeItem<>();
        newItem.setValue("Item " + this.tree.getExpandedItemCount());

        this.tree.getRoot().getChildren().add(newItem);
        this.tree.requestFocus();
        this.tree.getSelectionModel().select(newItem);
        this.tree.edit(newItem); //this should be enough, no?
    }
}

Steps to reproduce:
1. start the application
2. press the button "create item"
3. every button press creates a new item, *but* it is not editable.

If TreeView#layout() is called immediately before TreeView#edit it is working as expected.